The object of the invention is an arrangement in a rotor of an electrical machine and a method in the manufacture of the rotor of an electrical machine.
In electrical machines, the windings are usually placed in the slots located in the inner surface of the stator and the outer surface of the rotor. The slot winding is made of coils that are placed in the slots of the stator or the rotor. The coil consists of many conducting wire layers. The coil sides are connected together by the coil ends located at the ends of the slots.
The coil ends of the electrical machine rotors require a reinforcing structure against radial forces created when the rotor rotates. The reinforcement is usually made by winding fiberglass, Kevlar or carbon fiber tape or steel wire to the coil ends. When winding, the rotor is rotated around its axis of rotation and fiber is wound around the coil ends from the feed coil through the heating stage and guide roller. A support cylinder is installed inside the coil ends in order to create pre-tension in the wound reinforcement binding. An edge tape is installed before winding so that the wound tape will not spread. The edge tape is often made by resinifying a hard ring of fiberglass. Reinforcement by winding is presented in U.S. Pat. No. 6,029,338.
Reinforcement by winding is time-consuming. Manufacturing time is also spent on the furnacing, heating or tin coating in the reinforcement process. Because of the complexity, reinforcement by winding is also sensitive to variations in quality.
The durability of the reinforcement of the rotor coil ends is really tested in situations in which the rotation speeds, mass of the coil end of the rotor or diameter are big. For instance, the required rotation speed range considering wind power generators is large. Wind speed may quickly rise in gusts of wind, in which case the force directed to the binding trebles quickly. When the load leaves the network, the rotation speed of the rotor may quickly rise to 75-100% of the nominal speed.
The durability of large speeds is not good in reinforcements by winding. The winding material properties are one reason for this.